DESCRIPTION (applicant's abstract): We have identified the existence of mitochondrial uncoupling protein 2 (UCP2) in homeostatic circuits of healthy rodents and non-human primates. We also showed that ectopic expression of this uncoupling protein is induced in different models of neurodegeneration, including models of Parkinson's disease, hypoxia, epilepsy or trauma-induced brain injury. The expression of UCP2 in these experiments was associated with subpopulations of neurons and microglial cells at the site of the degenerative processes and predicted cells with the longest survival after the initial insult. In our preliminary studies, UCP2 overexpressing animals had diminished levels of free radical production in the brain and responded to transection of the entorhinal pathway with suppressed caspase 3 activation. We hypothesize that the induction of UCP2 in neurons and glial cells during pathological neurodegeneration is an attempt to protect and rescue injured neurons. Three Specific Aims are proposed to test this hypothesis: Specific Aim 1 To determine the role of the UCP2 gene product in intracellular calcium homeostasis and protection of cells in vitro by studying PC12 cells and primary cultures of retinal ganglion cells with and without UCP2 transfection and primary cultures of retinal ganglion cells taken from UCP2 transgenic, UCP2 knockout and wild type mice. The effects of oxygen and glucose deprivation and glutamate agonists will be assessed on cell death patterns and intracellular calcium metabolism in these cultures. Specific Aim 2 To determine the pattern of neurodegeneration, mitochondrial uncoupling activity, cytokine and ATP production in the brains of UCP2 knockout mice, UCP2 overexpressing transgenic mice and wild type mice undergoing hypoxia-, seizure- or 1-methyl-4-phenyl- 1,2,5,6 tetrahydropyridine (MPTP)-induced neurodegeneration. Specific Aim 3 To assess the effects on phenotype development of superoxide dismutase 2 knockout animals that are crossbred with either UCP2 knockout or UCP2 overexpressing mice. In these experiments, we will follow the phenotypic alterations by assessing neuronal loss, level of mitochondrial uncoupling activity, cytokine, free radical and ATP production and intracellular calcium levels using morphological, biochemical and molecular biological approaches. The results of the proposed studies will shed light on a novel mitochondrial mechanism that plays critical roles in the suppression of neurodegeneration regardless of the initial cause of disease. This will furnish one common target for the development of drugs against a variety of neurodegenerative pathologies, including those associated with hypoxia, epilepsy, Parkinson's, Alzheimer's and Huntington's Disease.